Gas pressure thermometer versus temperature sensor (Kitchen physics with phyphox)

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I was inspired by

Kitchen Physics: Lessons in Fluid Pressure and Error Analysis

Rebecca Elizabeth Vieyra, Chrystian Vieyra, and Stefano Macchia,

Phys. Teach. 55, 87 (2017); doi: 10.1119/1.4974119

Of course I did not want to put my smartphone to a jar and expose it to extreme kitchen conditions. Anyway my smartphone do not have necessary sensors: neither pressure nor temperature. And it is difficult to find a jar sufficiently large for it. But I got a SensorTag (thanks to Julien) which has all sensors that I need so much. The SensorTag is sufficiently small to get into my smallest jar and its price is sufficiently low not to be ruined by its eventual loss.

Thanks to numerous examples of phyphox I could program the SensorTag as I wanted. So I programmed measurements of temperature and pressure at the same time slower (1s per point) and added a p,T phase diagram. I had also to change readings of the temperature from unsigned to signed, otherwise at T<0°C temperature became infinitely large… I will not show the screen captures and will go to treated result (Python).

I thought that pressure p and temperature T would follow the same curve taking into account pV = nRT (V = const). It was not so, and not only due to a different delay of cooling in the refrigerator and heating in the oven (preheated slightly). There is a remarkable difference even when both p and T have stabilized..

I compared also measured T and Tp = pV/nR of the hermetic jar as a gas thermometer.

Figures:

1. Jar in the refrigerator.

2. p and T as functions of time.

3. p,T diagram.

P.S. The SensorTag is still operational.